WO2006120586A2

WO2006120586A2 - Lighting system comprising 2d led stack

Info

Publication number: WO2006120586A2
Application number: PCT/IB2006/051099
Authority: WO
Inventors: Egbert Lenderink; Peter A. Duine; Johannes A. A. M. Van Heeswijk
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2005-04-13
Filing date: 2006-04-11
Publication date: 2006-11-16
Also published as: JP2008536283A; US20080205077A1; CN101160544A; EP1875300A2; TW200734747A; WO2006120586A3

Abstract

The invention relates to a lighting system (LSI) which comprises a plurality of light engines (LEa1,l, LEa2,l, LEa3,l) and a system-exit window (OS). Each light engine comprising a first predetermined number of light emitting diodes, a second predetermined number of dichroÊc beam splitters, and an engine-output window. The light engine superposes light emitted by the light emitting diodes via at least one dichroÊc beam splitter on the engine-output window. The lighting system further comprises a plurality of light guides (LGa1,l, LGa2,l, LGa3,l) for guiding light emitted by the light engines towards the system-exit window. The light guides comprise a light-guide-output window (OGa1,l, OGa2,l, OGa3,l) The plurality of light-guide-output windows is arranged in an array constituting the system- exit window. The light guides enable the light engines to be located remotely from the system-exit window. This enables an effective cooling of the light emitting diodes of the light engines while allowing the light-guide-output windows to be stacked adjacent in the system- exit window.

Description

Lighting system comprising 2D LED stack

FIELD OF THE INVENTION

The invention relates to a lighting system comprising a plurality of light engines and a system-exit window, each light engine comprising a first predetermined number of light emitting diodes, a second predetermined number of dichroϊc beam splitters, and an engine-output window.

The invention further relates to a lamp and a display device.

BACKGROUND OF THE INVENTION

High intensity lighting systems usually comprise high-pressure discharge light sources to provide a high intensity output required in these high intensity lighting systems. However, high-pressure discharge light sources have several disadvantages. For example, the light intensity or the color of high-pressure discharge light sources is relatively difficult to influence. Another disadvantage is that a lighting system which comprises a high-pressure discharge light source is often vulnerable for light source failure, which may impact safety, especially when the lighting system is used in, for example, traffic light applications.

High brightness semiconductor light emitters, like Light Emitting Diodes (further also referred to as LED) have become available and are applied more often in high intensity lighting systems. A trend seems to be to apply an array of LEDs, which together form the high intensity light source. Often the outputs of different colors of LEDs are mixed to be able to provide substantially white light from the lighting system. In lighting systems, which comprise LEDs, the output of the LED is typically influenced by the ambient temperature of the LED: thus the ambient temperature of a LED often is a critical parameter in lighting systems, which comprise LEDs.

One example of a lighting system, which comprises a plurality of Light Emitting Diodes, is known from US patent application US 2004/0080938. In this patent application a theatrical or studio lighting system is based on a two dimensional array of light source cubes. Each light source cube comprises three light sources which are preferably directly applied to three different input surfaces of the light source cube. The three light sources preferably represent a LED triad, having one red, one green and one blue light source. The light source cube is a dichroϊc prism cube (also known as Philips prism arrangement), which comprises two dichroϊc coatings. Each dichroϊc coating reflects or transmits light selectively depending on, for example, the wavelength of the light. By choosing appropriate dichroϊc coatings within the known light source cube, the light of each of the three light sources is superposed on a single light output Surface of the light source cube.

In a lighting system which comprises a two dimensional array of light source cubes, it is rather difficult to effectively cool the LEDs applied to the different input surfaces of the light source cubes.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a lighting system which provides a two dimensional array of light source outputs wherein each light source combines the output of a plurality of light emitting diodes and wherein the light emitting diodes can be cooled relatively easily.

According to a first aspect of the invention the object is achieved with a lighting system comprising a plurality of light engines and a system-exit window, each light engine comprising a first predetermined number of light emitting diodes emitting light of a primary color distinct from the primary color of any of the other light emitting diodes in the same light engine, each light emitting diode being provided with a collimator having a longitudinal axis, each light engine further comprising a second predetermined number of dichroϊc beam splitters, and an engine-output window, wherein light emitted by each of the light emitting diodes is superposed on the engine-output window via at least one of the dichroϊc beam splitters, the lighting system further comprising a plurality of light guides for guiding light emitted by the light engines towards the system-exit window,each light guide having a light-guide-output window, the system-exit window being constituted by an array of light-guide-output windows.

The effect of the measures according to the invention is that the plurality of light guides enables the light engines to be located remotely from the system-exit window. The array of light-guide-output windows of the light guides can be closely stacked in the system-exit window without having an effect on the cooling of the light engines. The light engines are located remotely and can be arranged such that the LEDs can be effectively cooled. The light engines comprise dichroϊc beam splitters. Generally dichroϊc beam splitters split light of a light beam into different beams comprising different primary colors. In the light engines according to the invention the beam splitters are used to combine light of different primary colors and superpose the light of different primary colors on the engine- output window.

In an embodiment of the system, the light emitting diodes within each light engine are arranged along a straight line, substantially perpendicular to the longitudinal axis. A benefit of this embodiment is that it further facilitates the cooling of the LEDs, because, for example, a flow of air along to the straight line can be applied for cooling all LEDs within a light engine.

In an embodiment of the system, the light emitting diodes in each light engine are arranged on a single substrate. A benefit of this embodiment is that it enables a single heat sink to be applied to the substrate thus further simplifying the cooling of the LEDs in the light engines. In an embodiment of the system, the substrates of each light engine are arranged parallel. A benefit of this embodiment is that the cooling of the LEDs in each light engine can be concentrated at one location within the lighting system, for example, at one side of a cover of the lighting system. This arrangement of the light engines, for example, enables a design of the cover such that improved cooling characteristics are assigned to that part of the cover of the lighting system.

In an embodiment of the system, the light-guide-output windows are arranged within the array to form a surface substantially covering the system-exit window. A benefit of this arrangement is that the light-guide-output window can be placed adjacent to each other and thus substantially completely fill the system-exit window. In the known lighting systems, light source cubes are used which comprise three LEDs. The three LEDs are arranged at three input surfaces of each light source cube. When a two dimensional array of light source cubes is formed, some of the LEDs are arranged between two light source cubes which prevents these light source cubes from being placed adjacent to each other within the two dimensional array. The output window of a prior art illumination system, which is formed by an array of light output surfaces of the light source cubes cannot be completely filled with light output Surfaces of the light source cubes.

The lighting system according to the invention comprises light guides, which guide the light from each of the light engines to the light-guide-output windows. By using light guides having a light-guide-output window, the LEDs are located remotely not influencing the arrangement of the light-guide-output windows within the array. The light- guide-output windows are placed adjacent within the array and thus the system-exit window can be substantially completely filled.

In an embodiment of the system, each collimator reduces an angular distribution of the emitted light by the light emitting diodes to within 20 degrees with respect to the longitudinal axis of the collimator. A benefit of this embodiment is that the collimator enables an effective use of LEDs, which have an emission characteristic with a relatively broad angular distribution with dichroϊc beam splitters. The dichroϊc beam splitters reflect or transmit light selectively depending on, for example, the wavelength of the light and also, for example, on an angle of incidence between the light and the dichroϊc layer. Typically the dichroϊc beam splitter is designed for an optimum angle of incidence at which the dichroϊc beam splitter reflects or transmits light selectively with a relatively high efficiency. The efficiency of the dichroϊc beam splitter typically decreases for angles of incident, which are away from the optimum angle of incident. When using the collimator as claimed, the angular distribution of the emitted light is reduced to within 20 degrees and preferably to within 15 degrees from the optimum angle resulting in a relatively high overall efficiency of the dichroϊc beam splitters used in the light engines.

In an embodiment of the system, each light guide comprises a rigid light guide for substantially preserving the angular distribution of the light from the collimator. When a flexible light guide would be employed, the angular distribution of the guided light would be typically broadened while guiding the light from the light engine towards the system-exit window. For most light applications, such as spotlights, a narrow angular distribution is preferred. The use of a collimator narrows the angular distribution of the emitted light to, for example, within 15 degrees. The use of a rigid light guide substantially preserves the angular distribution, providing a lighting system having substantially the same overall angular distribution as provided by each one of the collimators.

In an embodiment of the system, the system comprises at least two dichroϊc beam splitters, wherein two dichroϊc beam splitters are combined into a single beam splitting cube. A benefit of this embodiment is that it enables a compact arrangement of the dichroϊc beam splitters and thus enables a compact design of the lighting system.

In an embodiment of the system, each light engine comprises three light emitting diodes. A benefit of using three LEDs is that it enables the creation of substantially every color, including white. These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

Fig. 1 shows two embodiments of the lighting system according to the invention, in which a first light guide guides the output of a first light engine to a system-exit window of a lighting system,

Fig. 2 shows an embodiment of the lighting system according to the invention, in which a second light guide guides the output of a second light engine towards the system- exit window of the lighting system,

Fig. 3 shows an embodiment of the lighting system according to the invention, in which a third light guide guides the output of a third light engine to the system-exit window of the lighting system, and Fig. 4 shows a lamp and a display device according to the invention.

The figures are purely diagrammatic and not drawn to scale. Particularly for clarity, some dimensions are exaggerated strongly. Similar components in the figures are denoted by the same reference numerals as much as possible.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the figures, items which may be arranged within an array are reference by suffixes i and j. The suffice i represents a row within the array and the suffice j represents a column within the array. References comprising the suffice i or j are used for generic description of the items they refer to and references in which the suffice i or j is replaced by a number are used for referring to specific items within the array.

Fig. 1 shows two embodiments of the lighting system LSI (see Fig. Ic), LS2 (see Fig. Id) according to the invention in which a first light guide LGay guides the output of a first light engine LEa_{1 j} to a system-exit window OS (see Fig. Ic, Id and Ie) of a lighting system LSI, LS2. Fig. Ia shows a side view of the first light engine LEay comprising three light emitting diodes R, G, B as light sources. In operation the LEDs R, G, B within the first light engine LEa_{1 j} each provide light of a primary color distinct from the primary color of any of the other LEDs R, G, B. In this embodiment one LED R emits red light (also indicated as red LED R), one LED G emits green light (also indicated as green LED G) and one LED B emits blue light (also indicated as blue LED B). Of course also other combinations of primary colors can be used. Each LED R, G, B is provided with a collimator Co having a longitudinal axis Ca. The collimator Co reduces an angular distribution of the light emitted by the LEDs R, G, B, for example, to within 20 degrees and preferably to within 15 degrees with respect to the longitudinal axis Ca of the collimator Co. The first light engine LEay further comprises two dichroϊc beam splitters Dl, D2, a first mirror Ml and an engine-output window OEa. The first dichroϊc beam splitter Dl reflects light emitted by the red LED R and transmits light emitted from the green LED G. The second dichroϊc beam splitter D2 reflects light emitted by the blue LED B and transmits light emitted from both the green LED G and the red LED R. Fig. Ia also shows the first light guide LGa_{1 j} with a light-guide-output window OGa_{1 j}. The first light guide LGay guides the light output of the first light engine LEa_{1 j} to the light-guide- output window OGay.

In Fig. Ia, the main light path of light emitted by the green LED G is indicated with a solid line. The emitted green light passes through the collimator Co which narrows the angular distribution of the green light. Next, the green light reflects at the mirror Ml towards the engine-output window OEa, passing through the first dichroϊc beam splitter Dl and the second dichroϊc beam splitter D2. The main light path of light emitted by the red LED R is indicated by a dash-dot line. The emitted red light passes through the collimator Co which narrows the angular distribution of the red light. Next, the red light reflects at the dichroϊc beam splitter Dl towards the engine-output window OEa, passing through the second dichroϊc beam splitter D2. The main light path of light emitted by the blue LED B is indicated by a dotted line. The emitted blue light passes through the collimator Co which narrows the angular distribution of the blue light. Next, the blue light reflects at the dichroϊc beam splitter D2 towards the engine-output window OEa. The arrangement of the first mirror Ml and of the two dichroϊc beam splitters Dl, D2 enables the light emitted by each of the three LEDs R, G, B to be superposed on the light output Surface OEa of the first light engine LEay creating light output S which is a mixture of the green light, the red light and the blue light. The light output S is guided by the first light guide LGay to the light-guide-output window OGay. The dimension d_a of the first light guide LGay may be adapted without departing from the scope of the invention. Fig. Ib shows a side view of the first light engine LEay in which a collimator extension Ce is added at the exit of each collimator Co. The collimator extension enables an extension of the distance between the LEDs and the mirror Ml or the dichroϊc beam splitters Dl, D2. Fig. Ic shows a side view of the lighting system LSI according to the invention in which an array of first light engines LEa₁^ LEa^₁, LEa₃₎₁, provides light to an array of first light guides LGa_1)l5 LGa^₁, LGa₃₎₁. The light guides LGa_1)l5 LGa^₁, LGa₃₎₁ guide the output of each of the first light engines LEa₁^ LEa^₁, LEa₃₎₁ to the light-guide- output windows OGa_1)l5 OGa^₁, OGa₃₎₁. The dimensions d_a of the light guides LGa_1)l5 LGa^₁, LGa₃₎₁ facilitate an arrangement of the first light engines LEa₁^ LEa^₁, LEa₃₎₁ such that the LEDs R, G, B can effectively be cooled while allowing an adjacent arrangement of light- guide-output windows OGa_1)l5 OGa^₁, OGa₃₎₁ at the lighting system-exit window OS. In the embodiment of the lighting system LSI as shown in Fig. Ic, the LEDs within each first light engine LEa_1)l5 LEa^₁, LEa₃₎₁ are arranged on a substrate SuI. The substrate SuI further comprises a heat sink HsI. The array of light-guide-output windows OGa_1)l5 OGa^₁, OGa₃₎₁ forms the system-exit window OS of the lighting system. A front view of the lighting system LSI is shown, for example, in fig. Ie. From both Fig. Ic and Fig. Ie it will be clear that each first light engine LEa_1)l5 LEa^₁, LEa₃₎₁ comprises a substrate SuI and that the system-exit window OS of the lighting system is constituted by a two dimensional array of light-guide- output windows OGa₁^ ...OGa₃₎₄.

Fig. Id shows a side view of a further lighting system LS2 according to the invention in which an array of first light engines LEa₁^ LEa^₁, LEa₃₎₁, provides light to an array of first light guides LGa_1)l5 LGa^₁, LGa₃₎₁. Again, the dimensions d_a of the light guides LGa_1)l5 LGa^₁, LGa₃₎₁ enable an arrangement of the first light engines LEa₁^ LEa^₁, LEa₃₎₁ such that the LEDs R, G, B can effectively be cooled while allowing an adjacent arrangement of light-guide-output windows OGa_1)l5 OGa^₁, OGa₃₎₁ at the lighting system-exit window OS. In the embodiment of the lighting system LS2 as shown in Fig. Id all LEDs of the first light engines LEa₁^ LEa^₁, LEa₃₎₁ arranged in a single column of the lighting system LS2 are arranged on a single substrate Su2. This has been achieved by using collimator extensions Ce at the appropriate collimators Co. The substrate Su2 also comprises a heat sink Hs2. Also in this lighting system LS2, the array of light-guide-output windows OGa_1)l5 OGa^₁, OGa₃₎₁ forms the system-exit window OS of the lighting system LS2. A front view of the lighting system LS2 is shown, for example, in Fig. Ie. From both Fig. Id and Fig. Ie it will be clear that each column of first light engines LEa_1)l5 LEa^₁, LEa₃₎₁ comprises a substrate Su2 and that the system-exit window OS of the lighting system LS2 is constituted by a two dimensional array of light-guide-output windows OGa₁^ ...OGa₃₎₄.

Fig. 2 shows an embodiment of the lighting system LS3 according to the invention in which a second light guide LGby guides the output of a second light engine LEby towards the system-exit window OS of the lighting system LS3. Fig. 2a shows a side view of the second light engine LEby comprising three light emitting diodes R, G, B, each providing light of a primary color distinct from the primary color of any of the other LEDs R, G, B. Each LED R, G, B is provided with a collimator Co which reduces the angular distribution of the light emitted by the LEDs R, G, B, similar to the arrangement shown in Fig. Ia. The second light engine LEby further comprises two dichroϊc beam splitters D2, D3, arranged in a dichroϊc prism cube, a first mirror Ml, a second mirror M2 and a system-output window OEb. The dichroϊc beam splitter D2 reflects light emitted by the blue LED B and transmits light emitted from the green LED G and from the red LED R. The second dichroϊc beam splitter D3 reflects light emitted by the green LED G and transmits light emitted from both the blue LED B and the red LED R. Fig. 2a also shows the second light guide LGby, which comprises a light-guide-output window OGby. The second light guide LGby guides the output of the second light engine LEby to the light-guide-output window OGby.

In Fig. 2a, the main light path of light emitted by the green LED G is indicated with a solid line. The emitted green light passes through the collimator Co towards the second mirror M2 which reflects the green light towards the dichroϊc beam splitter D3. The dichroϊc beam splitter D3 reflects the green light towards the engine-output window OEb, passing through the dichroϊc beam splitter D2. The main light path of light emitted by the red LED R is indicated by a dash-dot line. The emitted red light passes through the collimator Co and is transmitted by the dichroϊc beam splitter D2 and the dichroϊc beam splitter D3 towards the engine-output window OEb. The main light path of light emitted by the blue LED B is indicated by a dotted line. The emitted blue light passes through the collimator Co towards the first mirror Ml which reflects the blue light towards the dichroϊc beam splitter D2. The dichroϊc beam splitter D2 reflects the blue light towards the engine-output window OEb, passing through the dichroϊc beam splitter D3. The arrangement of the first mirror Ml, the second mirror M2 and of the two dichroϊc beam splitters D2, D3 enables the light emitted by each of the three LEDs R, G, B to be superposed on the light output Surface OEb of the second light engine LEby creating light output S which is a mixture of the green light, the red light and the blue light. The light output S is guided by the second light guide LGby to the light-guide-output window OGby. The dimensions d^, d_b2 of the second light guide LGby may be adapted without departing from the scope of the invention.

Fig. 2b shows a side view of the lighting system LS3 according to the invention in which an array of second light engines LEb₁^ LEb^₁, LEb₃₎₁, provides light to an array of second light guides LGb_1)l5 LGb^₁, LGb₃₎₁. The light guides LGb_1)l5 LGb^₁, LGb₃₎₁ guide the output of each of the second light engines LEb₁^ LEb^₁, LEb₃₎₁ to the light-guide- output windows OGb_1)l5 OGb^₁, OGb₃₎₁. The dimensions d^, d_b2 of the light guides LGb_1)l5 LGb2,i, LGb₃₎₁ enable an arrangement of the second light engines LEb₁^ LEb^₁, LEb₃₎₁ such that the LEDs R, G, B can effectively be cooled while allowing an adjacent arrangement of light-guide-output windows OGb_1)l5 OGb^₁, OGb₃₎₁ at the lighting system-exit window OS. In the embodiment shown in Fig. 2b, all LEDs of the second light engines LEb₁^ LEb₂^, LEb₃₎₁ are arranged on a single substrate Su3. The substrate Su3 further comprises a heat sink Hs3. The array of light-guide-output windows OGb_1)l5 OGb^₁, OGb₃₎₁ forms the system-exit window OS of the lighting system. A front view of the lighting system LS3 is shown, for example, in Fig. 2c. From both Fig. 2b and Fig. 2c it will be clear that in the embodiment shown in Fig. 2 the LEDs of each second light engine LEb_1)l5 LEb^₁, LEb₃₎₁ can be arranged on the same substrate Su3 and that the system-exit window OS of the lighting system LS3 is constituted by a two dimensional array of light-guide-output windows OGb₁^ ...OGb₃₎₄. Fig. 3 shows an embodiment of the lighting system LS4 according to the invention, in which a third light guide LGci _j guides the output of a third light engine LEci _j to the system-exit window OS of the lighting system LS4. Fig. 3a shows a side view of the third light engine LEcy comprising three light emitting diodes R, G, B, each providing light of a primary color distinct from the primary color of any of the other LEDs R, G, B. Each LED R, G, B is provided with a collimator Co which reduces the angular distribution of the light emitted by the LEDs R, G, B, identical to the arrangement shown in figs. Ia and 2a. The third light engine LEcy further comprises two dichroϊc beam splitters Dl, D4, a first mirror Ml and an engine-output window OEc. The dichroϊc beam splitter Dl reflects light emitted by a red LED R and transmits light emitted from a green LED G. The second dichroϊc beam splitter D4 reflects light emitted by both the green LED G and the red LED R and transmits light emitted by the blue LED B. Fig. 3a also shows the third light guide LGcy, which comprises a light-guide-output window OGcy. The third light guide LGcy guides the output of a one-dimensional arrangement of light engines LEc₁J (see Fig. 3c) to the light-guide- output window OGcy.

In Fig. 3 a, the main light path of light emitted by the green LED G is indicated with a solid line. The emitted green light passes through the collimator Co towards the first mirror Ml which reflects the green light towards the dichroϊc beam splitter D4, passing through the dichroϊc beam splitter Dl. The dichroϊc beam splitter D4 reflects the green light towards the engine-output window OEc of the third light engine LEcy. The main light path of light emitted by the red LED R is indicated by a dash-dot line. The emitted red light passes through the collimator Co towards the dichroϊc beam splitter Dl which reflects the red light towards the dichroϊc beam splitter D4. The dichroϊc beam splitter D4 reflects the red light towards the engine-output window OEc. The main light path of light emitted by the blue LED B is indicated by a dotted line. The emitted blue light passes through the collimator Co and is transmitted by the dichroϊc beam splitter D4 towards the engine-output window OEc. The arrangement of the first mirror Ml and of the two dichroϊc beam splitters Dl, D4 enables the light emitted by each of the three LEDs R, G, B to be superposed on the light output Surface OEc of the third light engine LEcy creating light output S which is a mixture of the green light, the red light and the blue light. The light output S is guided by the third light guide LGcy to the light-guide-output window OGcy.

Fig. 3b shows a side view of an embodiment of the lighting system LS4 according to the invention in which an array of third light engines LEc₁^ LEc^₁, LEc₃₎₁, provides light to an array of third light guides LGc_1)l5 LGc^₁, LGc₃₎₁. In the shown embodiment, each light guide LGc_1)l5 LGc^₁, LGc₃₎₁ guides the output of a one dimensional arrangement of third light engines LEc₁J LEc₂J, LEc₃J (only LEc₁J is shown in Fig. 3c) to the light-guide-output windows OGc_1)l5 OGC^₁, OGC₃₎₁. The dimensions Cl₀₁, d_c2 of the light guides LGc_1)l5 LGc^₁, LGc₃₎₁ enable an arrangement of the one dimensional arrangement of third light engines LEc₁J LEc₂J, LEc₃J such that the LEDs R, G, B can effectively be cooled while allowing an adjacent arrangement of light-guide-output windows OGc_1)l5 OGc^i, OGc₃₎₁ at the system-exit window OS of the lighting system LS4. In the embodiment shown in Fig. 3b, the LEDs of the one-dimensional arrangement of third light engines LEc₁J LEc₂J, LEc₃J are arranged on a single substrate Su4. The substrate Su4 further comprises a heat sink Hs4. The array of light-guide-output windows OGc_1)l5 OGc^i, OGc₃₎₁ forms the system-exit window OS of the lighting system LS4. A front view of the lighting system LS4 is shown, for example, in Fig. 3c.

Fig. 3c shows the front view of the embodiment of the lighting system LS4 shown in Fig. 3b.

Fig. 4 shows a lamp L and a display device DD according to the invention. Fig. 4a shows a lamp L comprising a cover Lc, a cooling section C, a hinge H and an exit window OL. The exit window OL of the lamp L comprises the system-exit window OS of the lighting system LSI, LS2, LS3, LS4 according to the invention. The heat sink HSl, HS2, HS3, HS4 of the lighting systems shown in the previous figures are concentrated at the cooling section C of the cover Lc. Typically the cooling section C is designed such that improved cooling characteristics are assigned to that part of the cover Lc. Fig. 4b shows a display device DD comprising a display Di and the lighting system LSI, LS2, LS3, LS4 according to the invention for illuminating the display Di. The display Di of the display device DD may, for example, be a Liquid Crystal panel or, for example, a partially transparent picture for use in a billboard. The first light guide LGaij, the second light guide LGbij and the third light guide LGcy are embodiments of light guides used in the lighting system LSI, LS2, LS3, LS4 according to the invention. The light guides LGay, LGby, LGcy enable an arrangement of the light engines LEa_{1 j}, LEby, LEcy in the lighting system LSI, LS2, LS3, LS4 such that the LEDs R, G, B, inside the light engines LEay, LEby, LEcy can be located remotely from the system-exit window OS, enabling the LEDs to be cooled effectively while allowing an adjacent arrangement of light-guide-output windows OGay, OGby, OGcy at the system-exit window OS of the lighting system LSI, LS2, LS3, LS4. The light guides LGay, LGb_{1 j}, LGcy, for example, comprise a dielectric material in which the light output S of the light engines LEay, LEby, LEcy is confined through total internal reflection. The dielectric material may be flexible or rigid.

Different combinations of light engines LEay, LEby, LEcy and light guides LGay, LGby, LGcy can be designed by the skilled person without departing from the scope of the invention.

LEDs can be light sources of distinct primary colors, such as, for example the well-known red (R), green (G), or blue (B) light emitters. In addition, the light emitter can have, for example, amber, magenta or cyan as primary color. These primary colors may be either generated directly by the light-emitting-diode chip, or may be generated by a phosphor upon irradiance with light from the light-emitting-diode chip.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims.

In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

CLAIMS:

1. Lighting system (LS 1 , LS2, LS3, LS4) comprising a plurality of light engines

(LEay, LEby, LEcy) and a system-exit window (OS), each light engine (LEay, LEby, LEcy) comprising a first predetermined number (N) of light emitting diodes (R, G, B) emitting light of a primary color distinct from the primary color of any of the other light emitting diodes (R, G, B) in the same light engine (LEay; LEby; LEcy), each light emitting diode (R, G, B) being provided with a collimator (Co) having a longitudinal axis (Ca), each light engine (LEay, LEby, LEcy) further comprising a second predetermined number (M) of dichroϊc beam splitters (Dl, D2; D2, D3; Dl, D4), and an engine-output window (OEa, OEb, OEc), wherein light emitted by each of the light emitting diodes (R, G, B) is superposed on the engine-output window (OEa, OEb, OEc) via at least one of the dichroϊc beam splitters (Dl, D2; D2, D3; Dl, D4), the lighting system (LSI, LS2, LS3, LS4) further comprising a plurality of light guides (LGay, LGby, LGcy) for guiding light emitted by the light engines (LEay, LEby, LEcy) towards the system-exit window (OS), each light guide (LGay, LGby, LGcy) having a light-guide-output window

(OGay, OGby, OGcy), the system-exit window (OS) being constituted by an array of light-guide- output windows (OGay, OGby, OGcy).

2. A lighting system (LSI, LS2, LS3, LS4) as claimed in claim 1, wherein the light emitting diodes (R, G, B) within each light engine (LEay, LEby, LEcy) are arranged along a straight line, substantially perpendicular to the longitudinal axis (Ca).

3. A lighting system (LSI, LS2, LS3, LS4) as claimed in claim 2, wherein the light emitting diodes (R; G; B) in each light engine (LEay; LEby; LEcy) are arranged on a single substrate (SuI).

4. A lighting system (LSI, LS2, LS3, LS4) as claimed in claim 3, wherein the substrates (SuI, Su2) of each light engine (LEay, LEby, LEcy) are arranged parallel.

5. A lighting system (LSI, LS2, LS3, LS4) as claimed in claim 2, wherein the light emitting diodes (R, G, B) of all light engines (LEay, LEby, LEcy) are arranged on a single substrate (Su3).

6. A lighting system (LSI, LS2, LS3, LS4) as claimed in claim 1 or 2, wherein the light-guide-output windows (OGay, OGby, OGcy) are arranged within the array to form a surface substantially covering the system-exit window (OS).

7. A lighting system (LSI, LS2, LS3, LS4) as claimed in claim 1 or 2, wherein a light guide (LGay, LGby, LGcy) guides light emitted by a plurality of light engines (LEay, LEby, LEcy) towards the system-exit window (OS).

8. A lighting system (LSI, LS2, LS3, LS4) as claimed in claim 1 or 2, wherein each collimator (Co) reduces an angular distribution of the emitted light by the light emitting diodes (R, G, B) to within 20 degrees with respect to the longitudinal axis (Ca) of the collimator (Co).

9. A lighting system (LSI, LS2, LS3, LS4) as claimed in claim 8, wherein each light guide (LGay, LGby, LGcy) comprises a rigid light guide (LGay, LGby, LGcy) for substantially preserving the angular distribution of the light from the collimator (Co).

10. A lighting system (LSI, LS2, LS3, LS4) as claimed in claims 1 or 2, comprising at least two dichroϊc beam splitters (Dl, D2; D2, D3; Dl, D4), wherein two dichroϊc beam splitters (D2, D3) are combined into a single beam splitting cube (Cu).

11. A lighting system (LSI, LS2, LS3, LS4) as claimed in claim 1 or 2, wherein each light engine (LEay, LEby, LEcy) comprises three light emitting diodes (R, G, B).

12. A lamp (L) comprising the lighting system (LSI, LS2, LS3, LS4) as claimed in claim 1 or 2.

13. A display device comprising the lighting system (LSI, LS2, LS3, LS4) as claimed in claim 1 as backlight illumination system.